TOF camera systems should not only comprise systems that ascertain the distances directly from the time of flight, but, in particular, also all the TOF camera systems, or 3D-TOF camera systems, which capture runtime information from the phase shift of an emitted and received radiation. PMD cameras with photonic mixer detectors (PMD) are especially suitable as TOF cameras or 3D-TOF cameras, as described in the applications EP 1 777 746, U.S. Pat. No. 6,587,186 and also DE 197 04 496, among others, and available, for example, from “ifm electronic GmbH” or “PMD Technologies GmbH” as the Frame Grabber 03D or as CamCubes. The PMD camera allows, in particular, a flexible arrangement of the light source and of the detector, which can be arranged in a housing as well as separately. Of course, cameras or devices with at least one receiving pixel should also be included in the term camera, or camera systems, like the applicant's distance measuring device O1D.
As described in detail in DE 197 04 496, in order to ascertain a distance or a corresponding phase shift of the reflected light the PMD sensor mixes the reflected light with the modulated signal. This mixture emits an in-phase signal (0°) and a signal shifted by 180°, from which a distance can be ascertained in a known manner. To improve the quality of the distance measurement the transmission modulation can be specifically shifted by 90°, 180° or 270° and preferentially ascertains a phase angle of the reflected signal relative to the transmitted signal by means of an IQ (in-phase, quaternary) demodulation. This procedure, in particular, is useful to capture redundant data in order to compensate, for example, different parasitic effects, such as fixed pattern noise (FPN), background light or asymmetries of the sensor.